The optical fiber communication is a main transmission means of a modern communication network; the optical fiber communication is that: At a sending end, transferred information is firstly converted into an electric signal, and then modulated onto a laser beam emitted by a laser, so that intensity of light changes with an amplitude change of the electric signal, and then sent out through an optical fiber; and at a receiving end, a detector converts an optical signal into the electric signals after receiving the optical signal, and restores the original information after demodulation. A distributed feedback (Distributed Feedback, DFB) laser adopts a distributed diffraction grating to generate single-wavelength output, and has advantages of a relatively simple manufacturing process, a small spectral line width, and so on; and is widely applied in the fields of dense wavelength division multiplexing (Dense Wavelength Division Multiplexing, DWDM) and optical fiber access network.
Output wavelength of the DFB laser is directly related to a grating, therefore, not only a change of outside temperature, but also an increase of current carrier density in the laser leads to a change of a central wavelength of the grating, thereby leading to a change of laser emitting wavelength. When a directly modulated digital signal is exerted on the DFB, because injection current corresponding to a “1” signal is different from injection current corresponding to a “0” signal, different peaks, that is, chirp, appear on an output spectrum after the signal is directly modulated. In the optical fiber, dispersion is a basic feature of the optical fiber, that is, for light with different wavelengths, propagation rates are different in the same optical fiber. Therefore, for the laser with the chirp, because of broadening of pulse, inter-symbol interference appears among the signals after a certain distance of transmission, which severely limits a transmission distance.
In the prior art, in order to suppress the chirp, a narrow band filter is added after the DFB laser, so that the filter filters the “0” optical signal while allowing a signal needed in the DFB laser to pass through, thereby weakening an effect of the dispersion on signal transmission. However, in this solution, because two different components and different materials are used, and because of different requirements for temperature, humidity, stress and so on in different environments, that a wavelength of the optical filter may be aligned with the signal wavelength of the DFB laser at all times cannot be ensured; furthermore, on the other hand, spacing between two peaks of a DFB spectrum is very small and at magnitude of 10 GHz, this requires a pass band of the optical filter to be very thin, which increases difficulty of implementing precise and real-time alignment between the two.